1. Field of the Invention
This invention relates to an acceleration detecting device which is a device to detect acceleration of an object and that is favorable for sensing collision of a vehicle and causing to activate a passenger protection apparatus such as an airbag and a seat belt.
2. Related Art
Conventionally, a device which mechanically assesses acceleration information by a rotor with a weight center of gravity and rotational center caused to be eccentric and makes output to an external portion as an electrical signal by a contact which rotates integrally with the rotor, as seen in Japanese Patent Application Laid-open No. 2-168525 Patent Gazette, is known as one device of this type. In this case, a single function is assigned to every one part: the rotor rotates due to the action of acceleration, a spring urges the rotor to prevent operation at times other than acceleration action, and the contact performs relaying to output the rotation of the rotor as an electrical signal.
However, assigning a single function to every one part causes the number of parts to increase, and mechanical connections also increase. Additionally, assurance of the spacing of contact points is structurally difficult, and so there exist problems of a lack of stability in quality, and an inability to make the acceleration detecting device compact and lightweight.
Additionally, in a case where an acceleration detecting device is applied in an airbag apparatus, it is necessary to send signals to the driver seat side, passenger seat side, and the like, and so a plurality of independent electrical signals may be output in some cases. There exists two possible methods for this: dividing the acquired electrical signal as the first method, and using two or more devices as a second method. However, the first method requires a transistor and constant-current circuit in an accessory system, resulting in complexity and high cost, and with the second method, cost is not only increased by two times or more, but it is difficult to obtain electrical signals having identical characteristics; problems exist with either method.
In addition, in a case where a casing of an acceleration detecting device is formed with resin material, assembly performance during press-fitting is poor, and in particular, there exists the problem wherein damage such as splitting of the cover occurs in a case of press-fitting with the cover remaining tilted.